In the manufacture of continuous glass strands by mechanical attenuation of glass from a bushing, the filaments are drawn at a uniform linear speed and are generally wound on sleeves supported by cylindrical mandrels, called collets, with the help of a traverse guide or similar distribution device which provides for substantially even distribution lengthwise of a sleeve. The filaments coming out of the bushing are grouped either in a single strand wound on a single sleeve, or in several strands wound simultaneously on several sleeves placed end to end on the same collet. For reasons of productivity, it is particularly important to assure the continuity of this operation.
In order to do this, when the desired quantity of strand has been wound onto the first collet, the collet is shifted from the work position, while the attenuation of the strand is continued. A second, empty collet, already rotating, then takes the place of the first, picks up the strand which is still being attenuated, and assumes the winding. In certain particular cases, the strands can be picked up directly and separately by each sleeve. In more customary fashion, on turret winders, the strands which have been temporarily regrouped in the course of attenuation are picked up in a special zone at the end of the empty collet, and then each strand is led back onto its own sleeve in order to begin a new winding.
The operating sequence is therefore the following:
placing the empty collet in rotation; PA1 lateral ejection of the strands on the end of the full collet; PA1 inversion of the position of the collets by rotation of the turret which supports them; PA1 fastening the strands onto the empty collet; and removal of the strand on its respective sleeve. PA1 ejected together on the end of the collet; PA1 ejected separately on the ends of their respective sleeves; or PA1 simply removed from contact by the distribution device (traverse oscillators, opposite which the strands remain without being subjected to their action). PA1 a means for forcing the strands between the two collets until the transfer occurs; PA1 a means for bringing the strand forcing means into action at the time the collets exchange position.
In what follows, we call "transfer" the phenomenon or action of fastening the strand onto the empty collet (or the empty sleeve) and "transfer operation" the operations whose general outline has just been given above.
There is a simple process for assuring the transfer by rapid deceleration of the full collet in arriving at the rest position, while the empty collet in reaching the work position turns at normal strand winding speed. Because of the increasing difference between the two speeds, the empty collet finally takes precedence because the adhesive forces between the surface of the collet and the strand become greater than the traction applied by the full collet; a loop is formed between the two collets, which is immediately held tight by adhesion on the empty collet, beginning the winding process onto the latter. See U.S. Pat. No. 3,409,238 for an apparent illustration of this process.
According to U.S. Pat. No. 1,809,660 a knife is introduced very rapidly between the two collets during their exchange in such a way as to cut artificial silk thread; the trailing end of the thread, separated from the full collet, is held tight under the thread originating from above.
Transfer can be obtained directly on the sleeve, but it is more easily effected if performed at the end of the collet on a special portion formed as a highly polished cylindrical extension.
The transfer process described above is also applicable to winders winding more than two strands simultaneously, the transfer being made as a whole for all the strands which are regrouped if there is room. However, the process will work only for certain strands. In effect, for a given attenuation speed, the traction applied by the full collet increases in proportion to the number of filaments. Over a certain limit, the drawing by adhesion still remains less than the attenuation force which must continue to be exerted, and the transfer of the strand onto the empty collet is thus not effected, for when the count of the strand increases, the entrainment by adhesion does not increase proportionately, because the filaments which make up the strand are bundled and do not all have contact with the surface of the empty collet, and also because the strand is more rigid.
This is why many other solutions, more complex and thus more expensive, have been subsequently proposed. Generally, however, they have proved to be imperfect in a variety of ways.
The end of the collet, for example, has been equipped with a circular plate. At the end of the ejection step, the strand is wedged into an orifice at the circumference bounded by the plate and the end of the collet as the first winding is made.
If the plate is held close by elastic forces, its tension should be low enough so that each strand enters the orifice, and sufficiently strong to keep it there after its entrance. In view of the important differences which can exist between one strand and another, there must be provision for adjustment in the majority of cases. Besides, the orifice must be cleaned by hand to remove the strand held tight at the end of each transfer operation. Also proposed is a definite control of the plate, associated with cleaning of the orifice by the action of a liquid under pressure. But, because of its complexity, this last device is expensive to make and to maintain.